Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes or tubes, although it can be made out of other materials. The basic materials are tubes, couplers and planks.
Planks provide a working surface for users of the scaffold. Conventionally, planks are made of seasoned wood and come in a variety of heights, are a standard width and are a maximum of 10 feet long. The board ends are protected by plates called hoop irons or nail plates, which are made of metal, steel or alloy steel.
Conventional scaffold planks are made of wood or lumber that over time, deteriorate. What is desired is a scaffold plank, and a process of making same, that overcomes the deficiencies of wood or lumber planks.
Fiberglass is a material made from extremely fine fibers of glass. It is used as a reinforcing agent for many polymer and plastic products; the resulting composite material, is known as fiber-reinforced plastic (FRP).
The types of fiberglass most commonly used are mainly E-glass (alumino-borosilicate glass with a small amount of alkali oxides, mainly used for glass-reinforced plastics), but also A-glass (alkali-lime glass with little or no boron oxide), E-CR-glass (alumino-lime silicate with a small amount of alkali oxides, has high acid resistance), C-glass (alkali-lime glass with high boron oxide content, used for example for glass staple fibers), D-glass (borosilicate glass with high dielectric constant), R-glass (alumino silicate glass without MgO and CaO with high mechanical requirements), and S-glass (alumino silicate glass without CaO but with high MgO content with high tensile strength).
The basis of textile-grade glass fibers is silica, SiO2. In its pure form it exists as a polymer, (SiO2)n. It has no true melting point but softens at 2,000° C. (3,630° F.), where it starts to degrade. At 1,713° C. (3,115° F.), most of the molecules can move about freely. If the glass is then cooled quickly, it will not form an ordered structure. In the polymer, it forms SiO4 groups that are configured as a tetrahedron with the silicon atom at the center and four oxygen atoms at the corners. These atoms then form a network bonded at the corners by sharing the oxygen atoms.
Although pure silica is a perfectly viable glass and glass fiber, it must be worked with at very high temperatures, which is a drawback unless its specific chemical properties are needed. It is usual to introduce impurities into the glass in the form of other materials to lower its working temperature. These materials also impart various other properties to the glass that may be beneficial in different applications. The first type of glass used for fiber was soda lime glass or A glass but it was not very resistant to alkali. A new type of glass, E-glass, was formed. E-glass is an alumino-borosilicate glass that is substantially alkali free (<2%). This was the first glass formulation used for continuous filament formation.
The letter E is used because it was originally for electrical applications. S-glass is a high-strength formulation for use when tensile strength is the most important property. C-glass was developed to resist attack from chemicals, mostly acids that destroy E-glass. T-glass is a North American variant of C-glass. A-glass is an industry term for cullet glass, often bottles, made into fiber. AR-glass is alkali-resistant glass. Most glass fibers have limited solubility in water but are very dependent on pH.
Chloride ions will attack and dissolve E-glass surfaces. Since E-glass does not melt, but softens, the softening point is defined as “the temperature at which a 0.55-0.77 mm diameter fiber 235 mm long, elongates under its own weight at 1 mm/min when suspended vertically and heated at the rate of 5° C. per minute”. The strain point is reached when the glass has a viscosity of 1014.5 poise. The annealing point, which is the temperature where the internal stresses are reduced to an acceptable commercial limit in 15 minutes, is marked by a viscosity of 1013 poise.
Occupational Safety and Health Administration (OSHA) Regulation set forth at 29 CFR 1926.451 discusses scaffold requirements. It provides, except as otherwise provided, a scaffold and scaffold component shall be capable of supporting, without failure, its own weight and at least 4 times the maximum intended load applied or transmitted to it. Much or the load is applied to the planks. Applied loads are measured in pounds per square foot (psf).